Our research has focused on the role of the complement system in the host's defense against infection. We have examined three separate but related aspects of the complement system and its interaction with microorganisms. First, we are studying the role of complement in anti-viral immunity. Second, we are examining the interaction of the third component of complement (C3) and the surface of encapsulated organisms. Third, we have identified a colony of dogs with a genetically determined deficiency of C3 and have begun studies on its genetic basis and its biological consequences.